Our studies on specific evolutionary and genetic problems continues using Drosophila as a test organism. (1) Our studies on the mechanism of DNA replication and repair have uncovered ca 11 X chromosome loci which are sensitive to methyl methane sulfonate (MMS). One such mutant is defective in "excision repair" and at least two in "postreplication repair." We are now examining MMS sensitive mutants on the 3rd chromosome. (2) We have uncovered a system for producing so-called insertion mutants at selected loci on the X chromosome by utilizing so-called male recombination (MR) chromosomes isolated in nature. (3) Strains of Drosophila selected for tolerance to alcohol appear related to the amount of alcohol dehydrogenase (ADH) produced and thus may be instructive in the realm of genetic regulation. We have purified ADH and are "fingerprinting" variants. (4) Male sterility for use in controlling insect populations is being investigated with a series of different male sterile mutants. We found one mutant in which the sterile sperm displaced fertile sperm almost immediately. (5) Courtship studies of Hawaiian Drosphila species are underway using field collected animals. Allozyme variation in these Drosophila is under study.